Files

T

ocrampal 9e517eb122 Update 2026-06-29-biological-reference_v16.md

2026-06-30 10:53:28 +02:00

29 KiB

Raw Blame History

Tripartite Synapse — Biological Reference (companion to v16 pseudocode)

Companion to tripartite_synapse_v16_pseudocode.md · principle: logic_principles_v3. v16 gives NIGHT a hierarchy of homeostatic actors at scales above the single synapse, and a phased structure. The actors of consolidation are not the actors of transmission: by day the six local components transmit; by night a hierarchy — astrocyte territory, the whole neuron, and (as an external signal) the assembly/network — renormalizes and reallocates. Early-night cycles downscale the day's transient changes (synaptic homeostasis); later cycles consolidate the survivors. Occupancy filled by day (receptor surface, channel coupling) is returned to baseline each night, so only what was written into a structural ceiling persists.

The three synaptic components and their support structures

A SYNAPSE is composed of three first-class components:

PRE — presynaptic bouton (the axon's terminal at this synapse)
POST — postsynaptic spine (the dendrite's terminal at this synapse)
ASTRO — astrosynapse, the perisynaptic astrocytic process (the astrocyte's terminal)

Each has an upstream support structure that supplies it:

AXON supplies PRE (transmission + transport from soma)
DEND supplies POST (integration + transport from soma)
the astrocyte cell body supplies ASTRO (energy + ECM material)
SOMA is the integrating center and the root of neuronal material

The compartment analogy: AXON:PRE = DEND:POST = astrocyte-body:ASTRO = supply line : terminal.

Resource variables

DAY budget (one per component)

Aggregates fast energy AND fast consumables — everything needed to run moment-to-moment.

pre_budget — ATP for VGCC gating, vesicle fusion (SNARE), VATPase vesicle refill, plus fast consumables: vesicle membrane lipids, synaptotagmin recycling.
post_budget — ATP for the NaK pump (membrane reset after current), NMDA current handling, plus fast actin monomers for transient spine changes and receptor-recycling lipids.
dend_budget — ATP for bAP propagation (NaK reset along branch), local translation (ribosome running cost), SERCA Ca²⁺ resequestration, plus fast mRNA consumed by translation.
soma_budget — ATP for AP generation (Na⁺/K⁺ currents + NaK reset), CREB phosphorylation, nuclear Ca²⁺ handling, plus shipping running costs.
axon_budget — ATP for AP propagation at nodes of Ranvier, kinesin/dynein motor running cost, fast myelin maintenance.
astro_central_budget — ATP from glycolysis at the astrocyte cell body; funds EAAT clearance, serine→D-serine synthesis, lactate export, fast process motility.

astro_lactate[i]

Lactate exported from the astrocyte cell body to synapse i. Biologically: glucose → (glycolysis) → lactate, released into extracellular space, absorbed by neuronal MCT2 transporters, converted to pyruvate → TCA → ATP in the neuron's mitochondria. The astrocyte is the primary fast-energy supplier to pre, post, and dend.

NIGHT energy (one per component) — NOT recoverable

ATP for structural assembly. Distinct from DAY budget because it is spent on building, and the work of assembly is thermodynamically gone once done (cannot be recovered by disassembly).

pre_energy: RIM/Munc13 incorporation, VGCC clustering.
post_energy: CaMKII anchoring, actin polymerization, PSD scaffold remodeling.
dend_energy: mitochondria incorporation, cytoskeletal reinforcement.
soma_energy: ribosome biogenesis, ion-channel incorporation.
axon_energy: myelination, microtubule stabilization.
astro_energy: process retraction, ECM secretion, racemase upregulation.

NIGHT material (one per component) — RECOVERABLE

Slow structural proteins. Recoverable because disassembly (LTD) returns the proteins to a reusable pool (ubiquitin-proteasome → amino acids; internalized receptors → endosomal reserve).

soma_material (root) — all neuronal structural proteins from CREB-driven synthesis: AMPA subunits, PSD scaffold, AZ scaffold, mRNA transcripts (Arc, BDNF), organelles.
dend_material — from soma: Arc/plasticity mRNA, mitochondria, cytoskeletal proteins, AMPA subunits in transit to spines.
post_material — from dend: AMPA receptor subunits (GluA1/2), PSD scaffold (PSD-95, SHANK, Homer), structural actin, CaMKII.
axon_material — from soma: kinesin/dynein motors, microtubule components, myelin proteins.
pre_material — from axon: RIM, Munc13, VGCC subunits, structural vesicle proteins.
astro_material (root: astrocyte cell body) — EAAT proteins, serine racemase, ECM proteins (Glypicans, Thrombospondins), process cytoskeleton.

Why energy and material are separate in NIGHT but combined in DAY: during DAY both are fast consumables replenished on the same timescale, so one budget variable suffices. During NIGHT they diverge — material is recoverable after LTD, energy is not — so they must be two variables. This asymmetry (material returns to the pool, energy is gone) is what makes one synapse's depression genuinely fund another's potentiation.

Structural variables (strength ceilings — written in NIGHT)

Each aggregates several correlated structural properties into one capacity.

pre_structure — active zone capacity: slot_ceiling (number of vesicle docking slots) + VGCC_coupling (Ca²⁺-channel proximity to slots, sets release efficiency) + refill_ceiling (max RRP replenishment rate).
post_structure — spine sensitivity capacity: slot_ceiling (number of PSD anchoring slots for AMPA) + spine_volume (local reserve and actin machinery) + reserve_ceiling (endosomal AMPA pool size).
dend_structure — branch capacity: bAP_fidelity(position) (mitochondrial density sets propagation strength, attenuates with distance) + translation_ceiling (local mRNA capacity) + transport_speed (cytoskeletal integrity).
soma_structure — somatic output capacity: baseline_threshold (inverse: ion-channel density at axon initial segment) + AP_reliability (Na⁺ channel density) + synthesis_ceiling (ribosome density + CREB machinery).
axon_structure — axonal capacity: propagation reliability (myelination density) + transport_ceiling (motor density + microtubule integrity) + mitochondrial density.
astro_structure — astrosynaptic environmental capacity: perisynaptic_distance⁻¹ (wall proximity — closer = more glutamate contained) + EAAT_density (clearance ceiling) + Dserine_tonic (baseline co-agonist) + ECM_integrity. Self-reinforcing both directions: tighter wrap + more tonic D-serine make future potentiation easier; looser wrap + zero tonic D-serine make future depression easier.

Budget ceilings (endurance ceilings — written in NIGHT)

{component}_budget_ceiling — the maximum fuel the component can hold / the maximum duration of sustained behavior. Biologically: mitochondrial density and local fuel-storage capacity. Built by activity-driven mitochondrial biogenesis; lost by mitophagy when idle. Parallel to structure: structure is strength capacity, budget_ceiling is endurance capacity.

Trace variables

fast_trace (one per component) — DAY only, decays automatically

The local record of recent activity that biases the next behavior.

pre_fast_trace — residual presynaptic Ca²⁺ after spikes (τ≈100ms). Biases NT release (facilitation) and provides tagging eligibility.
post_fast_trace — spine Ca²⁺ amplitude × rise-speed (τ≈tens ms). Encodes the LTP-vs-LTD instruction (fast rise → CaMKII → potentiation; slow rise → phosphatase → depression).
dend_fast_trace — branch Ca²⁺ from bAP + spine spillover (τ≈300ms). Integrates branch co-activity.
soma_fast_trace — nuclear Ca²⁺ from each AP (τ≈seconds). Drives toward CREB activation.
axon_fast_trace — propagation load (τ≈seconds). High load → Na⁺ inactivation at branch points → propagation failure (this is axonal short-term depression).
astro_fast_trace — perisynaptic Ca²⁺ from mGluR5 activation by glutamate spillover (τ≈seconds). Drives D-serine release.

soma timing traces (emergent refractory + adaptation + alignment)

soma_Na_inactivation (τ≈ms) — sodium-channel inactivation after an AP. Its recovery IS the refractory period (emergent, not a hardcoded timer). High → absolute refractory; decaying → relative refractory; recovered → normal.
soma_adaptation (τ≈100s of ms) — slow K⁺ channel (SK/M-type) activation accumulating over a spike train, raising threshold. This is spike-frequency adaptation.
soma_refractory_alignment — deposited when a suprathreshold input arrives during refractoriness (a missed coincidence). Speeds future recovery so the soma aligns to its input rhythm. Bottom-up: no rhythm is represented; alignment emerges from accumulated local mismatches and decays when mismatches stop (self-limiting).

possible_tag (one per component) — intermediate, τ≈s–min

Graded accumulation of tagging eligibility. For POST, this is the CANDIDATE tag lifetime.

endurance_need (one per component) — intermediate, τ≈s–min

Deposited when budget depletion interrupts a behavior that was on a LOCALLY successful trajectory. Records that fuel — not structure, not significance — was the binding constraint on a forming success. Requires NO dopamine (homeostatic, not associative). Local success proxy per component (each uses only its own state + arrived signals):

PRE: own fast_trace high (was releasing strongly), optionally amplified by retrograde messenger (endocannabinoid / NO / BDNF) that has arrived.
POST: own Ca²⁺ climbing toward tagging threshold (naturally local).
DEND: own branch strongly active (high branch voltage/Ca²⁺) when propagation fell short.
SOMA: own nuclear Ca²⁺ climbing toward CREB.
AXON: own propagation load high (was carrying a strong train).
ASTRO: own local glutamate/Ca²⁺ high (was under heavy clearance/D-serine demand).

tag (one per component) — DAY→NIGHT bridge, τ≈hours

The validated record of significance that survives to NIGHT and gates strength commits. Formed by coincidence of local eligibility + non-local validation (dopamine). POST is special — two-phase, three coincidences:

CANDIDATE: local Ca²⁺ above threshold + astrosynapse D-serine present (coincidence 1).
amplified when bAP confirms soma fired (coincidence 2).
STABLE: CANDIDATE + dopamine within stabilization window (coincidence 3). Biologically: early CaMKII creates a labile tag (early-LTP); PKA driven by dopamine via D1R stabilizes it (late-LTP). Without dopamine, the candidate degrades — early-LTP reverses.

Behaviors — biological meaning

PRE | AP — neurotransmitter release

NT_flux = RRP × sat(pre_fast_trace, K_release) models continuous NT release proportional to the readily-releasable pool and a saturating Ca²⁺ drive (synaptotagmin's cooperative Ca²⁺ sensitivity, simplified to a saturating curve). RRP depletes as released (short-term depression as a consequence) and refills via VATPase (energy-throttled, so low budget deepens depression). The mGluR2/3 brake is presynaptic autoinhibition by spillover (Gi → reduced VGCC opening).

POST | NOT_bAP — three calcium sources, two plasticity cases

Source 1 (AMPA): glutamate opens AMPA → depolarizing current + small Ca²⁺; the depolarization begins ejecting the NMDA Mg²⁺ block.
Source 2 (NMDA): if depolarized enough (Mg²⁺ ejected) AND D-serine present (astrocyte co-agonist) AND glutamate bound → large Ca²⁺ influx. This is the coincidence detector.
Source 3 (bAP, separate context): back-propagating AP adds depolarization + Ca²⁺, amplifying an existing signal supralinearly.
Case 1 (STP): high Ca²⁺ drives AMPA receptors from the local reserve to the surface, bounded by the anchoring-slot ceiling. Fast, reversible, NO dopamine. When Ca²⁺ falls, receptors drift back — short-term depression as a passive consequence, never signaled.
Case 2 (LTP tag): high Ca²⁺ + (later) dopamine sets the tag that NIGHT uses to raise the slot ceiling. NIGHT builds slots; DAY fills them.

DEND | bAP — bidirectional signaling

Propagates the bAP from soma toward spines (fidelity attenuates with distance — distal spines get weaker confirmation, are harder to potentiate) and integrates spine signals toward the soma.

SOMA | AP — integration, firing, emergent timing

Fires when integrated branch input exceeds a threshold that is the baseline (from structure) raised by adaptation and modulated by neuromodulators, gated by the emergent refractory state. Each AP deposits three traces (inactivation → refractory, adaptation → threshold rise, nuclear Ca²⁺ → plasticity). The soma is the coincidence detector at the cellular scale (nuclear Ca²⁺ + dopamine → CREB), and the production bottleneck: its tag gates how much material all downstream components get in NIGHT.

AXON | AP — reliable propagation with frequency-dependent failure

Propagation reliability is set by myelination and degraded by high-frequency load (Na⁺ inactivation at branch points = axonal STD). The axon also transports material to boutons and sets the timescale of presynaptic structural commits.

ASTRO | CONTINUOUS — gatekeeper and energy hub

Clears glutamate (EAAT), supplies D-serine (the NMDA co-agonist that gates postsynaptic LTP), and distributes lactate to the territory by demand-weighting (active synapses generating more clearance load pull more fuel; slow synapses get less). The same spillover that excites the astrocyte (mGluR5 → Ca²⁺ → D-serine) also brakes the presynapse (mGluR2/3 → Gi) — one signal, opposite effects via different receptors. The astrocyte is the energy root and the gain control of the whole synapse.

NIGHT operations — biological meaning

Step 1 (replenish/distribute): overnight protein synthesis peaks (CREB-driven, gated by soma_tag — corresponds to slow-wave-sleep replay). Soma material flows to branches/axon then spines/boutons; astrocyte material flows to astrosynapses, tag-weighted.
Step 2 (strength commits): tagged components build structure — more slots, tighter coupling, tighter astrosynaptic wrap. Coherence bonus when pre+post+astro all tagged (the whole synapse agrees). astro_structure self-reinforces.
Step 2b (endurance commits): components with high endurance_need build budget_ceiling — mitochondrial biogenesis. Competes with step 2 for the same material/energy.
Step 3 (passive decay): both ceilings decay; maintenance from the remaining pool resists decay only where sufficient. Depotentiation and endurance-loss are both by neglect — no signal weakens anything; unmaintained capacity simply drifts down. Recovered material (not energy) returns to pools.
Step 4 (homeostatic scaling): if the soma fired too much overall, all synapses scale down proportionally (sleep-associated global downscaling), preserving relative differences.
Step 5 (clear traces): fast traces, possible tags, endurance needs, and soma timing traces reset; tags below expiry clear, above-expiry tags carry forward (multi-night consolidation); structure and budget_ceiling persist.

Shockwave lockdown

Emergency global astrocytic Ca²⁺ wave → GABA + ATP release → mass AMPA internalization and hyperpolarization. Bypasses budget gates. A circuit breaker against runaway excitation.

Pool-filling: private reserve vs contested supply

The pseudocode uses two filling primitives, distinguished by where the resource comes from.

fill (private reserve). The pool is replenished from a source the component owns outright, uncontested by siblings, bounded by the component's own ceiling and a rate cap.

RRP refill — vesicles mobilized from the bouton's own reserve pool toward the docking-slot ceiling, rate-limited by VATPase. The reserve is private to the bouton.
SOMA self-replenish — the soma fuels itself from its own mitochondria toward its budget ceiling. No other component draws on it.

refill (contested supply). The pool is replenished from a supply that multiple components compete for, rationed by demand (gap to ceiling).

pre/post/dend/axon budgets — drawn from astrocytic lactate (shared across all synapses the astrocyte wraps) plus shipment from soma/axon/dendrite (shared across downstream targets).

Neither primitive (their own forms). Some inflows are not fills toward a ceiling:

AMPA surface insertion — Ca²⁺-driven rate from the spine's private endosomal reserve, with an explicit passive drift-back (short-term depression) when Ca²⁺ is low. Not a steady fill.
D-serine release — demand-driven (saturating in astro Ca²⁺) and budget-limited, like NT release; a release process, not a pool top-up.
Root productions — glycolysis(glucose) at the astrocyte and CREB_synth(soma_tag) at the soma are the system's energy and material roots: raw inflows capped only by the external vascular supply, not fills toward an internal ceiling.

The distinction matters biologically: a private reserve guarantees a component some autonomy (the bouton can refill its RRP from its own vesicles even when lactate is scarce), while a contested supply couples a component's fate to its neighbours' demands (operational budget fails first where many active synapses compete for the same lactate).

PRE ↔ POST interaction: local computation, message-only coupling

The presynapse and postsynapse never read each other's internal state. They interact only by writing to and reading from shared cleft channels. Each side computes entirely locally on what it has: its own variables plus whatever signals have arrived in the cleft. This is the message-passing realization of the locality principle.

Forward channel — glutamate (PRE → POST and ASTRO). The presynapse writes glutamate via NT_flux. The postsynapse reads it (AMPA, NMDA) and the astrosynapse reads it (clearance, mGluR5). The astrosynapse clears it. PRE never knows whether POST responded — it only emits.

Gate channel — astro_Dserine (ASTRO → POST). The astrosynapse writes D-serine; the postsynapse reads it as the obligatory NMDA co-agonist. POST cannot open NMDA without this arrived signal, but it does not read the astrocyte's state — only the delivered D-serine.

Backward channel + — retro_NO (POST → PRE). When the postsynapse's NMDA opens (Mg²⁺ ejected, D-serine present, glutamate bound), nNOS — physically tethered to the NMDA receptor through PSD-95 — synthesises nitric oxide (and, on a slower timescale, BDNF is released). These diffuse retrogradely to the presynapse. Biologically this is the classic retrograde messenger of LTP: it tells the bouton that its release landed on a postsynapse that genuinely responded. In the model, POST emits retro_NO proportional to its own NMDA-driven calcium — computed purely from POST's local state — and PRE reads it as retro_NO_local.

retro_NO_local is exactly the grounding of the presynaptic endurance signal. The presynapse's local success proxy is "I was releasing strongly" (pre_fast_trace high). On its own that only says the bouton was working hard, not that the work mattered. retro_NO adds the missing confirmation — that the postsynapse responded — without PRE ever reading POST's calcium. So PRE deposits endurance need as pre_fast_trace × (1 + retro_NO_local): strong release that was confirmed effective makes the strongest claim that fuel, not futility, was what interrupted a forming success. retro_NO is short-lived (NO degrades and diffuses within seconds), so the channel decays fast — confirmation must be recent to count.

Backward channel − — retro_eCB (POST → PRE). When the postsynapse is strongly depolarised, it synthesises endocannabinoids (2-AG, anandamide) that diffuse retrogradely and bind presynaptic CB1 receptors, suppressing release. This is depolarisation-induced suppression of excitation (DSE) — a homeostatic negative feedback: an over-driven postsynapse tells the presynapse to release less. In the model, POST emits retro_eCB from its own membrane potential, and PRE reads it as retro_eCB_local, which reduces the release drive sat(...) × (1 - retro_eCB_local). Again POST computes from its own state; PRE adjusts from the arrived signal; neither reads the other's interior.

The two backward channels are opposite-signed messages the postsynapse sends about its own condition: retro_NO says "your input was effective — worth sustaining," retro_eCB says "I am saturated — ease off." Together with the forward glutamate and the D-serine gate, they make the synapse a fully message-coupled system of locally-computing components.

Why RRP refill is in NOT_AP only. During an AP the bouton releases — RRP depletes. Refill (VATPase reloading vesicles from the reserve pool) is a recovery process that proceeds between spikes. Placing fill(RRP, ...) only in the NOT_AP context makes the AP context pure depletion and the NOT_AP context pure recovery. A consequence falls out for free: during sustained high-frequency firing there are many AP steps and few NOT_AP steps, so RRP depletes faster than it recovers — short-term depression deepens with frequency, with no explicit depression rule. The release itself is throttled further when budget is low (VATPase refill is energy-limited), coupling metabolic state to the depth of depression.

Presynaptic short-term potentiation — VGCC coupling occupancy

VGCC_active is the presynaptic parallel to the postsynaptic AMPA_surface. Both are MEDIUM-tier occupancy variables: a current operating value filled toward a NIGHT-built ceiling, no dopamine, reversible, drifting back when undriven.

Biologically, VGCC_active represents the effective coupling between voltage-gated calcium channels and the vesicle docking slots — how reliably each calcium influx is converted into release. Repeated eligible activity (accumulated pre_possible_tag) transiently tightens this coupling — through calcium-channel facilitation, active-zone protein phosphorylation, and channel-to-sensor proximity changes — raising release efficiency without changing the number of channels (which is the structural ceiling pre_structure.VGCC_coupling, written only at NIGHT). When eligibility falls, the coupling relaxes back to baseline over seconds-to-minutes: presynaptic short-term depression as the passive consequence of undriven coupling, never a signalled act.

This gives the presynapse a genuine intermediate-timescale memory it previously lacked — a "this bouton has been reliably active lately" state that outlasts individual spikes and bursts, filling the gap between the fast trace (residual calcium, ~100 ms) and the tag (hours). It also completes the capacity/occupancy symmetry across the synapse: both PRE and POST now fill a MEDIUM occupancy variable toward a PERSISTENT structural ceiling, rather than PRE reading its ceiling directly as if capacity and occupancy were the same thing.

NIGHT as iterated NREM cycles — the biology

The distributed, cyclic NIGHT models sleep-dependent consolidation more faithfully than a single commit step.

Why cycles, not one event. NREM sleep proceeds in repeated cycles (the ultradian ~90-minute rhythm, and within it the <1 Hz slow oscillation with its up- and down-states). Protein synthesis, hippocampal–cortical replay, and synaptic renormalization all advance incrementally across these cycles rather than in a single consolidation moment. Modeling NIGHT as a loop of cycles captures this: each cycle is a small, local round of produce → transport → incorporate.

Production each cycle (the roots). The soma's CREB-driven transcription/translation produces a batch of structural material per cycle, gated by the soma's own tag (replay-driven activity). The astrocyte cell body produces a batch of energy (glycolysis) and ECM material per cycle, capped by glucose. These are the two roots; everything downstream lives on what they ship.

Transport over cycles (the descent). Material and energy move one hop down the supply chains per cycle — soma → dendrite/axon → spine/bouton; astrocyte body → astrosynapses — by the same motor transport that carries cargo by day, now at the consolidation timescale. A distal bouton on a long axon therefore receives its material only after several cycles, so its consolidation lags a proximal one. This is the NIGHT-scale image of the transit delay.

Incorporation and tag consumption (the commit). A tagged synapse incorporates arrived material into structure (more receptor slots, tighter active zone, tighter astrocytic wrap) or into budget capacity (mitochondrial biogenesis), spending energy on the assembly. The tag is consumed in proportion to what was built — the molecular tag (CaMKII/PKA-maintained eligibility) is discharged as capture completes. A strong tag is satisfied early; a marginal one waits for later cycles.

Two ways the night ends. Either the standing tags are all spent (consolidation finished — the rested case) or the night's metabolic budget is exhausted (ran out of night — the overloaded case). Unspent tags are not discarded: they persist (decaying slowly) into the next day and compete again the next night, so importance is re-tested across nights and a marginal memory may consolidate over several nights or, if it decays first, never.

Energy is the irreversible cost. Material released when an unmaintained structure is pruned returns to the pool and is reused; the energy burned to build or to prune is gone. Across a lifetime this energy throughput bounds how much the system can ever consolidate — the metabolic arrow of time underlying the whole model.

NIGHT's hierarchy of actors — the biology

Why the actors differ from DAY's. Transmission is local — a bouton releases, a spine integrates, an astrosynapse clears. Consolidation is not: it involves quantities no single synapse can see. Whether one synapse's strengthening "fits" depends on the neuron's total synaptic weight; reallocating metabolic support depends on an astrocyte's whole territory; deciding which memories to replay depends on assemblies of neurons. So NIGHT is enacted by actors at higher scales, each conserving a quantity at its scale.

The astrocyte territory (Tier 2). The astrocyte cell body supports hundreds to thousands of synapses. By day it allocates lactate by demand; by night it reallocates its produced energy and ECM material across its whole territory, biased by the demand it accumulated and by replay. This is a genuine territory-level actor — the astrocyte is the metabolic arbiter of its domain, and its nightly reallocation decides which of its synapses can afford to consolidate.

The neuron as a whole (Tier 1). Synaptic homeostasis (the synaptic homeostasis hypothesis of Tononi and Cirelli) operates on the neuron's total synaptic weight: across sleep, the cell's synapses are renormalized downward multiplicatively, preserving relative differences while restoring overall excitability and freeing capacity. This is a neuron-scale operation — no synapse can perform it, because no synapse knows the cell's total weight. In the model the neuron accumulates that total by day and renormalizes it by night, scaling all the cell's structures by a common factor when the total exceeds the cell's budget.

The assembly / network (Tier 0, external). Systems consolidation — hippocampal–cortical replay — reactivates the day's patterns across ensembles of neurons during NREM, and this dialogue selects which assemblies are written into cortex. This is a network-scale process beyond a single neuron, so the model treats it as an external arrived signal (replay_reweight), exactly as it treats dopamine and glucose. Fully modeling it requires a network of these neurons.

Occupancy downscaling — why only ceilings persist. During the day, synapses fill occupancy: receptors trafficked to the surface (AMPA_surface), calcium-channel coupling tightened (VGCC_active), eligibility accumulated (possible_tag). These are transient and reversible. If they carried across the night undiminished, a synapse could become lastingly strong without ever earning a tag or paying the consolidation cost — bypassing the entire validation machinery. Multiplicative-global downscaling during early-night cycles returns occupancy to baseline. A synapse that was tagged and had its ceiling raised starts the next day strong; one that merely filled occupancy during the day starts back at baseline. The relative potentiation survives only where it was written into structure — which is precisely synaptic homeostasis enforcing that the slow tier carries the learning and the fast/medium tier is renewed each day.

Why phased. A single sweep cannot both reset and build, because building should act on the post-reset landscape. Early cycles are subtractive (downscale occupancy, renormalize weight, make metabolic room); later cycles are additive (commit the survivors). This is the NREM arc — slow-wave-dominated downscaling early, selective consolidation later — and it makes each cycle's kind depend on where in the night it falls, so the cycles are genuinely different operations, not installments of one.

29 KiB Raw Blame History Unescape Escape